1. Field of the Invention
This invention relates to tags, especially marker tags for livestock, and has particular relevance to ear tags intended to be applied to cattle to indicate that an animal has passed a particular health inspection or test. It is an object of the invention to improve the "tamper-proof" qualities of the identification tags known hitherto.
An animal marked with an official identification tag may be considerably more valuable in the market place than one which is not so marked. It is therefore tempting for unscrupulous persons to obtain used ear tags, usually from slaughtered animals, to open the ear tags and then re-apply them to animals which have not passed the official inspection or test.
2. Description of the Prior Art
There have been previous attempts to devise a satisfactory form of tamper-proof ear tag. In our British patent specification No. 1 509 565 we described an ear tag for livestock comprising a strip doubled over into two limbs and having a hollow rivet blank standing up at the free end of one of the limbs, the rivet blank comprising a stock portion surmounted by a narrower neck portion, a receiver hole through the strip near to the free end of the other of the limbs, the receiver hole being large enough to accommodate the neck portion but not the stock portion, and the neck portion having a depth such that when it has passed through the receiver hole it can be curled out and back under itself to form a rolled bead. However, this earlier invention of ours has not proved entirely successful because it was difficult in practice to form a rolled bead on every tag and if the rolled bead was only partially formed there was a risk that the tag could be opened and re-used.
French patent specification No. 73.22752 describes various forms of ear tag of the "button" type consisting of a plastics plate bearing identification markings, a rivet and a plastics locking button to receive the rivet head. In the embodiment of FIG. 6 the rivet head is locked in position in the button by a spring steel washer. However, the rivet has a solid body and neck which could be cut across and subsequently rejoined by bonding, or fitting a dowel, the head of the rivet being retained in the enclosed button cavity. The rivet pierces the ear tissue but does not cut away any of the tissue and clogging of the locking mechanism with tissue or hair can result. A tag having a plate and button joined only by a cylindrical rivet can rotate in the hole in the ear, thus causing the hole to enlarge after a period of time, leading to a risk of the tag falling out.
British patent specification No. 1 053 454 describes a tag formed by two tabs joined by a solid probe. The probe may have a conical shank. In the embodiment of FIGS. 17 and 18, an aperture intended to receive the head of the probe has cuts around it to form resilient tongues. However, there is nothing to prevent the tabs being pushed towards one another and thus enable the resilient tongues to be loosened. There is no discussion of the problems involved in making a tag tamper-proof.
U.S. Pat. No. 2,940,199 describes various forms of ear tag which can be secured in position by hand. In the embodiment of FIGS. 5, 6 and 7 the female part of the tag has tongues which engage in a groove below the head of the hollow male part. However, this is not a tamper-proof tag and indeed reference is made to the possibility of separating the tags when required by the use of a pair of pliers.